phytoplankton of two river lakes in relation to flooding period

POLISH JOURNAL OF ECOLOGY
(Pol. J. Ecol.)
53 3 419–425 2005
Short research contribution
Władysława WOJCIECHOWSKA 1 , Agnieszka PASZTALENIEC 1 , Michał SOLIS 1 ,
Marek TURCZYŃSKI 2 , Jarosław DAWIDEK 2
1
Department of Botany and Hydrobiology, Catholic University of Lublin
Norwida 4, 20-061 Lublin, Poland, e-mail: sokol@kul.lublin.pl
2
Department of Hydrography, Maria Curie-Skłodowska University
Akademicka 19, 20-033 Lublin, Poland
PHYTOPLANKTON OF TWO RIVER LAKES IN RELATION TO
FLOODING PERIOD (RIVER BUG, EASTERN POLAND)
ABSTRACT: Studies were carrying out in
two shallow (mean depth ≈ 0.3 m) and small
(area 2.7–8.2 ha) river lakes, which were flooded
by water of River Bug (Eastern Poland) once a year
(in spring). The species composition, biomass of
phytoplankton and concentration of chlorophyll
a were studied. Samples were taken in June (after
flooding) and in August (after three months of
isolation from river water). About 150 species of
phytoplankton were determined. After the flood
period phytoplankton biomass was dominated
by nannoplankton belonging to Cryptophyceae
and Chrysophyceae (strategy-r) and in the stabilization
period by microplanktonic green and
blue–green algae (strategy-K). The higher biomass
and concentration of chlorophyll a values
were noted in August than in June. The differentiation
of phytoplankton was also stated between
near-by stations in both lakes.
KEY WORDS: river lakes, floodplain lakes,
phytoplankton, nannoplankton, microplankton,
River Bug
The valley of the River Bug (Eastern Poland)
is considered as one of the last natural
river valleys of Central Europe. The middle
part of River Bug (Lublin province) is unregulated
and runs in a valley differing in
width. It meanders strongly in many places
and tends to form the anastomosis (Chmiel
et al. 2003).
The valley is rich with many riparian
sites. Characteristic components of river
valley are river lakes, also called oxbow
lakes, which are periodically flooded (usually
in spring) by River Bug waters. Majority
of river lakes in Europe is under human
pressure and under strong eutrophication
changes (flooding by nutrient rich water
of river, fish farming as well as using lakes
for tourism). The decrease of macrophyte
density and decline the diversity of phytoplankton
are the symptoms of such changes
(Van den Brink et al. 1994, Amoros
2001).
The aim of the present study was to compare
species composition and phytoplankton
biomass in the period after the flood phase
(inflow of Bug River waters to river lakes)
and in the period of stabilization of conditions
(isolation phase) in 2004 year.
Studies were carried out in two river
lakes (Jama Roma and Orchówek) located
in the middle part of the Bug Valley and distant
from each other by 22 km. They belong
to meander lakes (Chmiel et al. 2003) with
mean depth ≈ 0.3 m, they are permanent water
bodies, filled by water all over year. The

420 Władysława Wojciechowska et al.
morphological parameters are presented in
Table 1 and bathymetry at Fig. 3.
These lakes are supplied with water
during a short-lasting, springtime flooding
by river, when the level of river water reaches
220 cm (Fig. 1). The total exchange of water
in lakes took 28 days. The first phase of the
hydrological activity in river lakes (inflow
and outflow) continued since 27 th of March
until 14 th of April. The second phase, a weaker
one, was characterizes only by outflowing
water from river lakes and it continued from
15 th until 23 rd of April (Fig.1). In the remaining
part of the year, lakes were supplied with
water from their own catchment area.
The catchment area of Lake Orchówek
(124.8 ha) is managed and built-up (Fig. 2).
The meadows and the farms are reaching the
river. In the lake itself, fish farming is performed.
The catchment area of Lake Jama Roma
(55 ha) has a more natural character; it is
covered with pine and alder trees (Fig. 2).
Records of River Bug water levels from
water-gauge of Institute of Meteorology and
Water Management were used. Bathymetric
maps were done in summer period by sonic
depth finder “Sonel” and measurements
points were localized by GPS with GARMIN
apparatus.
Biological and chemical studies (species
composition and biomass of phytoplankton,
concentration of chlorophyll a, TN and
TP) were conducted two times in 2004 year.
One set of samples was taken in 1 th of June
(the period after filling lakes by Bug waters)
and a second one at 30 th August (after three
months of isolation from river water, the period
of summer stabilization). In each of lake
two stations were selected which differed in
a depth (Fig. 3). Samples were taken using
Patalas-type water sampler and poured into
a collective sample from whole water column
at each station.
Total nitrogen and phosphorus (TN and
TP) were analyzed by spectrophotometric
methods after earlier mineralization as described
by Hermanowicz et al. (1999).
The concentration of chlorophyll a was
measured by a spectrophotometric method
(Nusch 1980). Biomass was estimated based
on the phytoplankton number using an inverted
microscope (by the way of Utermöhl)
and making the measurements of species
sizes. The calculations were done according
to Hillebrand et al. (1999). The algae species
were grouped in two size groups: nannoplankton
≤30 µm and microplankton above
30 µm according to Pavoni (1963). The
species diversity was estimated with Shannon-Weaver
index (1949) and evenness
index (Lloyd-Ghelardi 1964), according
to formulas:
H' = ∑ – (n i
/N • log n i
/N)
e = H'/H max ,
where
n i – numbers of a species i
N – total numbers of phytoplankton
H max = log 2
S, S – number of species
The physico-chemical parameters as SD,
pH and conductivity were measured every
time.
In both lakes at stations where depth
was greater than 3 m, the water transparency
was lower in August (0.8 m) than in June
(1.5 m).
There was a difference in value of chemical
parameters between lakes. The value of
water reaction and conductivity was greater
in Lake Orchówek. In Lake Orchówek, the
mean pH = 7.5, conductivity = 720 µS cm –1 ,
while in Lake Jama Roma – pH = 6.5, conductivity
= 550 µS cm –1 . The concentration of total
phosphorus and total nitrogen were high
in both lakes. In Lake Orchówek TP value
was about 0.08 mg dm –3 , significant greater
concentration of total phosphorus was noted
in Lake Jama Roma – 0.20 mg dm –3 . Total ni-
Table 1. Morphological parameters of studied lakes.
Lake
Area
(ha)
Volume
(m 3 )
Mean depth
(m)
Max. depth
(m)
Length of
shoreline
(m)
Orchówek 8.17 27793 0.34 2.85 2618
Jama Roma 2.68 8163 0.30 3.69 1481

Phytoplankton of river lakes in relation to flooding period
421
A B A
260
240
220
Water level of River Bug [cm]
200
180
160
140
120
100
80
60
Period of water exchange in lakes
03-11-01
03-12-01
04-01-01
04-02-01
04-03-01
04-04-01
04-05-01
04-06-01
04-07-01
04-08-01
04-09-01
04-10-01
Fig. 1. Changes of water level of River Bug in hydrological year 2004. A – isolation period (lack of contact
of lakes with river waters), B – through-flow period (contact of lakes with river waters), Arrows
indicate a date of sampling.
Fig. 2. Land use in the catchments of studied river lakes.

422 Władysława Wojciechowska et al.
Fig. 3. Bathymetric maps of river lakes and location of sampling stations.
%
Lake Orchówek
Lake Jama Roma
June August June August
100
80
60
40
20
0
1 2 1 2 1 2 1 2
microplankton
nannoplankton
Fig. 4. The share of nanno- and microplankton biomass in phytoplankton at 1–2 stations of both lakes.

Phytoplankton of river lakes in relation to flooding period
423
Table 2. Number of phytoplankton species in studied lakes.
Taxonomic group
Number of species
Lake Orchówek
Lake Jama Roma
Cyanoprokaryota 9 20
Euglenophyta 0 7
Dinophyceae 2 1
Cryptophyceae 4 6
Chrysophyceae 0 9
Bacillariophyceae 7 26
Chlorophyta 41 23
Table 3. Phytoplankton parameters in studied lakes (mean values for station 1 and 2).
Lake Orchówek
Lake Jama Roma
Parameters
June August June August
Chlorophyll a
33 65 68 131
(µg dm –3 )
Phytoplankton biomass
(mg dm –3 )
2 26 5 26
Shannon-Weaver index (H’) 1.90 1.49 2.23 1.21
Evenness index 0.54 0.39 0.56 0.30
dominant species
(percentage share of the species
in total phytoplankton biomass)
Cryptomonas
marssonii (37%)
Chlamydomonas
globosa (45%)
Pandorina
morum (39%)
Mallomonas
semiglabra
(28%)
Mallomonas tonsurata
(17%)
Anabaena oscillarioides
(53%)
Microcystis
flosque (33%)
trogen content was similar in both lakes and
reached about 2.50 mg dm –3 .
In both lakes a total of 155 different species
of planktonic algae were determined,
which belong to seven various taxonomically
groups (Table 2).
The difference in composition and quantity
of phytoplankton between two studied
periods was observed in both lakes. In the
first period (after flooding lakes by river water)
the fast-growing and disturbance-tolerant
nannoplanktonic species (r-strategists)
had greater contribution to phytoplankton
biomass (Fig. 4). The most of them belong
to mixotrophic species (Reynolds 1984).
Percentage share of nannoplankton in total
biomass was from 68 to 99% (Fig. 4). In Lake
Orchówek, Cryptophyceae was a dominate
group and Chlorophyta was the second group
characterized by great percentage share in
biomass (Fig. 5). In Lake Jama Roma Chrysophyceae
dominated and Cyanoprokaryota
species were the subdominants (Fig. 5). In
mentioned above taxonomic groups usually
two species were the most abundant, Cryptomonas
marssonii and Rhodomonas pusilla
(Cryptophyceae), Mallomonas semiglabra
and M. tonsurata (Chrysophyceae), Scenedesmus
obliquus and Staurastrum sp. (Chlorophyta).
Among Cyanoprokaryota the most
numerous was a small (2.5 µm in diameter),
two-celled species Synechocystis sp.
During the isolation period the percentage
share of microplankton in total phytoplankton
biomass significantly increased in
both lakes (Fig. 4). Species belonging to this
size-group were composed with mixed morphotypes
e.g. colonies or large unicells, all of
them are considered K-strategists (Reynolds
1984). In Lake Orchówek microplankton
was dominated (40–50%) by two Chlorophyta
species – Pandorina morum and
Closterium dianae. Despite microplankton
biomass increase, the great contribution

424 Władysława Wojciechowska et al.
Lake Orchówek
Lake Jama Roma
%
June A ugust June A ugust
100
80
60
40
20
0
1 2 1 2 1 2 1 2
Cyanoprokaryota
Chrysophyceae
Others
Cryptophyceae
Chlorophyta
Fig. 5. The share of taxonomic groups in biomass of phytoplankton at 1–2 stations of both lakes.
(≥ 50%) of nannoplankton was observed
(Fig. 4). It was the result of the development
of nannoplanktonic green alga – Chlamydomonas
globosa. In Lake Jama Roma the microplankton
contribution in biomass was
much greater (60–100%) and blue-green algae
Anabaena oscillarioides and Microcystis
flos-aquae were dominants (Table 3).
In both lakes the species diversity expressed
by Shannon-Weaver and evenness
indices was higher in June than in August
(Table 3). The higher species richness after
the river water flooding in similar type of
lakes was observed also by Garcia de Emiliani
(1993).
The phytoplankton abundance differs
between both studied periods. Total
biomass and chlorophyll a concentration
were characterized by lower values in June
(nannoplankton dominance) than in August
(microplankton dominance) (Table 3).
Total phytoplankton biomass was in June
2 mg dm –3 (L. Orchówek) and 5 mg dm –3
(L. Jama Roma) and chlorophyll a concentration
33 and 68 µg dm –3 respectively. In
August phytoplankton biomass in both lakes
reached the value (26 mg dm –3 ) many times
higher and concentration of chlorophyll in
Lake Orchówek was as high as 65 µg dm –3
and in Jama Roma – 131 µg dm –3 . The increase
of phytoplankton biomass and greater
percentage share of microplankton in the
isolation phase in shallow floodplain lakes
was stated by other authors (Garcia de
Emiliani 1993, de Oliveira and Calheiros
2000).
In both lakes phytoplankton differed between
studied stations (Fig. 5). In both lakes
the greater diversity of taxonomic groups
occurred at station 1 and clear domination
by one taxonomic class was observed at station
2 (Fig. 5). At station 2 in Lake Orchówek
the contribution of Cryptophycae (June) or
Chlorophyta (August) to total biomass was
higher than 90%, while in Lake Jama Roma
phytoplankton was dominated only by Cyanoprokaryota
species (60–100%). The considerable
differentiation between neighboring
stations in the oxbow lake was noted
by Wilk-Woźniak and Bucka (2004).

Phytoplankton of river lakes in relation to flooding period
425
The studies of phytoplankton confirmed
that river lakes belong to water bodies
in which the species diversity to a high
degree depends on supplying by river water.
The through flow of river water results in
water mixing in lakes and the increase of
nutrients content (Amoros 2001). According
to Reynolds (1984) these conditions
favorite the development of small opportunistic
r-selected species (like Cryptophyceae
and Chrysophyceae in studied river
lakes) characterized by rapid growth rate.
In the period of summer stabilization (after
three months isolation of lakes from the
river) species with r-strategy were succeeded
by large slow-growing forms of K-strategy
(f.e. Pandorina morum or Microcystis
flos-aquae).
ACKNOWLEDGMENTS: This work was supported
by the Polish State Committee for Scientific
Research (KBN grant 2 P04F 027 26).
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(Received after revising March 2005)